There is a possible supplier for Jolla 1 phone batteries. This news was initially announced on the German Jolla Community site https://jollausers.de/.
A German battery manufacture has been willing to produce a battery exactly fitting into the Jolla 1 phone.

Specs:

3 years warranty !!!!

real 2.100 mAh

63 x 50 x 5 mm * 39 gramms

Be aware that this battery isn't authorised by the Jolla company and in case the battery/phone combination will create a singularity in space(or does other harm) you will be held accountable for it.

@fmotl: Maybe for the point that this battery fits into the Jolla 1 phone by design not by accident as the others.
Maybe for the point that those are from a known source rather than of a not traceable origin.

2 Answers

The battery for the HTC desire 360 apparently is identical with the Jolla battery and can easily be bought for around 11 Euro. I tried it myself and the HTC desire battery works flawlessly in my Jolla 1. The only aspect I did not check so far is whether the temperature signal is reliable/usable.

And the good news is that they also ship abroad and it's not expensive
(Switzerland - so outside EU but still ground mail within continental Europe).

BTW: restriction on transport of lithium batteries is only for air mail, and phone batteries usually fall below the restriction limits (maybe there are a few exception for extremely power-hungry phablets). I've regularly ordered PDA and phone batteries from Hong-Kong (Air mail) through eBay without any problem.

Lithium transport limits might only come into play :

when there are temporary special measure in action (e.g.: total ban on air transport of lithium batteries, whenever there's a exploding battery scandal - like "Hoverboards", Samsung smartphones, Sony laptop batteries a decade ago, etc.)

when the company poorly interprets regulations (lithium battery need to be protected when transported - they need to be plugged into some protection circuitry. In modern Lithium-Polymer batteries for gadgets like smartphones and laptops, the protection circuitry is within the battery package itself. The battery is permanently soldered to it. That's why there are more than just 2 (pos/neg) connectors : extra connectors are for talking to this chip. But some postal services like SwissPost are just stupid, and require that the battery is plugged to a device - i.e.: you can't ship a battery unless it's transported inside the smartphone, even if the protection is already within the battery and the smartphone doesn't have any protection at all)

I'm a bit surprised though that this battery didn't come from Akku-King - Their secret motto seems to be "If it has a battery, we have a spare for it"